It’s easy to see where Tommy Nance can garner his fighter’s mentality from.

Nance’s journey from an undrafted prospect to a big-league player has been well documented, but the journey of his father, Mark, is just as impressive as the fight the younger Nance has gone through.

On a trip back home to surprise his parents in 2014, Tommy returned to an an empty house. He called his father, who was with the rest of the family visiting friends nearby.

That’s when Mark told Tommy that he was diagnosed with ALS.

While he had heard of ALS, Tommy didn’t fully understand the disease and what challenges it presents.

“[He] kinda gave me the lifespan statistics on it real quick,” Tommy said. “Cause I also had no idea what ALS was. When I did more and more research on it it was harder to grasp it and accept it.”

That didn’t stop Mark from fighting. For roughly 80% of people affected by ALS, the disease is terminal within 5 years. Seven years later, Mark is still fighting. And that spirit has been passed onto Tommy who battled to reach the majors. Mark and Tommy’s mother have been able to watch their son defy the odds and pitch in the big leagues.

“When he first called me, ‘[I] was like are you kidding me?’” Mark said. “I was in shock, tears. My wife Susan and I just hugged each other [and] were like, ‘Are you kidding me? I always believed you could do this.’”

For more on their incredible journey, watch the video above.